[[ Bug 20090 ]] Catch obj-c exceptions when called through LCB

runrevmark · runrevmark · commit ef5d18b08cec · 2017-09-04T12:25:04.000+01:00
This patch wraps the obj-c ffi call to objc_msgSend (and friends) in a @try/@catch block. Any obj-c exception which is thrown through this mechanism is caught and thrown as an MCError object containing the 'reason' for the error as the message.
diff --git a/docs/lcb/notes/20090.md b/docs/lcb/notes/20090.md
@@ -0,0 +1,6 @@
+# LiveCode Builder Language
+
+## Foreign Function Interface
+
+* Obj-C exceptions thrown from calls to obj-c foreign handlers will now be caught
+  and rethrown as an LCB error.
diff --git a/libscript/libscript.gyp b/libscript/libscript.gyp
@@ -29,6 +29,7 @@
 			'src/script-object.cpp',
 			'src/script-package.cpp',
 			'src/script-execute.cpp',
+			'src/script-execute-objc.mm',
 			'src/script-error.cpp',
 		],
 	},
@@ -73,6 +74,15 @@
 			
 			'conditions':
 			[
+				[
+					'OS != "mac" and OS != "ios"',
+					{
+						'sources!':
+						[
+							'src/script-execute-objc.mm',
+						],
+					},
+				],
 				[
 					'OS == "linux" or OS == "android"',
 					{
diff --git a/libscript/src/script-error.cpp b/libscript/src/script-error.cpp
@@ -369,6 +369,15 @@ MCScriptThrowJavaBindingNotSupported(void)
 								 nil);
 }
 
+bool
+MCScriptThrowForeignExceptionError(MCStringRef p_reason)
+{
+    return MCErrorCreateAndThrow(kMCGenericErrorTypeInfo,
+                                 "reason",
+                                 p_reason,
+                                 nil);
+}
+
 bool
 MCScriptThrowObjCBindingNotSupported(void)
 {
diff --git a/libscript/src/script-execute-objc.mm b/libscript/src/script-execute-objc.mm
@@ -0,0 +1,47 @@
+/* Copyright (C) 2017 LiveCode Ltd.
+ 
+ This file is part of LiveCode.
+ 
+ LiveCode is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License v3 as published by the Free
+ Software Foundation.
+ 
+ LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ for more details.
+ 
+ You should have received a copy of the GNU General Public License
+ along with LiveCode.  If not see <http://www.gnu.org/licenses/>.  */
+
+#include "libscript/script.h"
+#include "script-private.h"
+
+#include "ffi.h"
+
+#include "foundation-auto.h"
+
+#include <Foundation/Foundation.h>
+
+#include "script-execute.hpp"
+
+bool MCScriptCallObjCCatchingErrors(ffi_cif *p_cif, void (*p_function)(), void *p_result_ptr, void **p_arg_ptrs)
+{
+    @try
+    {
+        ffi_call(p_cif, p_function, p_result_ptr, p_arg_ptrs);
+        return true;
+    }
+    @catch (NSException *exception)
+    {
+        MCAutoStringRef t_reason;
+        if (!MCStringCreateWithCFString((CFStringRef)[exception reason], &t_reason))
+        {
+            return false;
+        }
+        
+        return MCScriptThrowForeignExceptionError(*t_reason);
+    }
+    
+    return false;
+}
diff --git a/libscript/src/script-execute.cpp b/libscript/src/script-execute.cpp
@@ -311,12 +311,13 @@ class MCScriptForeignInvocation
         else
             t_objc_msgSend = (void(*)())objc_msgSend;
 #endif
-        ffi_call(t_cif,
-                 (void(*)())objc_msgSend,
-                 p_result_slot_ptr,
-                 t_objc_values);
-        
-        return true;
+        /* We must use a wrapper function written in an obj-c++ source file so that
+         * we can capture any obj-c exceptions. */
+        extern bool MCScriptCallObjCCatchingErrors(ffi_cif*, void (*)(), void *, void **);
+        return MCScriptCallObjCCatchingErrors(t_cif,
+                                              (void(*)())objc_msgSend,
+                                              p_result_slot_ptr,
+                                              t_objc_values);
 #else
         return true;
 #endif
diff --git a/libscript/src/script-private.h b/libscript/src/script-private.h
@@ -682,6 +682,9 @@ MCScriptThrowMissingFunctionInForeignBindingError(void);
 bool
 MCScriptThrowUnableToLoadForiegnLibraryError(void);
 
+bool
+MCScriptThrowForeignExceptionError(MCStringRef p_reason);
+
 bool
 MCScriptThrowObjCBindingNotSupported(void);
 
diff --git a/tests/lcb/vm/interop-objc.lcb b/tests/lcb/vm/interop-objc.lcb
@@ -75,7 +75,6 @@ end handler
 
 ---------
 
-
 public handler TestObjInterop_RoundtripNumber()
 	if not the operating system is in ["mac", "ios"] then
 		skip test "objc binding succeeds" because "not implemented on" && the operating system
@@ -101,4 +100,25 @@ end handler
 
 --------
 
+__safe foreign handler MCHandlerTryToInvokeWithList(in Handler as any, inout Arguments as optional List, out Result as optional any) returns optional any binds to "<builtin>"
+__safe foreign handler NSArrayFirstObject(in pObj as ObjcId) returns ObjcId binds to "objc:NSArray.firstObject"
+
+private handler __CallNSNumberMethodOnNSString(in pString as ObjcObject) returns optional any
+	return NSArrayFirstObject(pString)
+end handler
+
+public handler TestObjcInterop_CatchObjcException()
+	if not the operating system is in ["mac", "ios"] then
+		skip test "objc exception handler succeeds" because "not implemented on" && the operating system
+		return
+	end if
+
+	variable tArguments as List
+	variable tResult as optional any
+	put [ StringToNSString("foo") ] into tArguments
+	test "objc exception is caught" when MCHandlerTryToInvokeWithList(__CallNSNumberMethodOnNSString, tArguments, tResult) is not nothing
+end handler
+
+---------
+
 end module
